Combination gas and oil burner



Oct. 8, 1957 P. LOOP 2,808,876

COMBINATION GAS AND OIL BURNER Filed Sept. 3, 1954 5 II b" Flloll IO -IS FIG. 2 V I/ FIG.3

INVENTOR PHILIPPUS LOOF HIS ATTORNEY Unite tates COMBINATION GAS AND OIL BURNER Application September 3, 1954, Serial No. 454,165

Claims priority, application Netherlands September 9, 1953 6 Claims. (Cl. 158-41) This invention relates to improvements in combination gas and oil burners, suitable for operation with either type of fuel separately, comprising a liquid fuel atomizer and a gas supply conduit terminating in an annular gas mouthpiece surrounding the atomizer.

Combination burners are widely used in industries such as petroleum refineries, wherein gaseous and liquid fuels are burned at different times, e. g., because of changing availability of one or the other of these fuels. One example, described in U. S. Patent No. 2,216,508, includes a central oil supply tube that carries an oil atomizer at the front end and is surrounded by a gas supply tube the front end of which terminates short of the front of the atomizer, there being a conical deflector or diffuser surrounding the oil tube to deflect the mixture of gas and primary air from the gas supply tube outwards at an angle of approximately to the direction in which secondary air is supplied outside of the gas tube. This results in an intimate mixing of the gas mixture with the secondary air. The outer diameter of the deflector is smaller than the inner diameter of the gas supply tube.

In operating the known type of combination burners on liquid fuel, there occurs a considerable amount of fouling of the annular gas passage, i. e., in the case of 40 the burner according to the said patent, the walls defining the channel through which the gaseous mixture flows prior to and during emergence from the mouthpiece. This fouling involves the deposition or formation of soot or coke on these walls to the extent that the burner cannot thereafter be operated satisfactorily on gas without cleaning.

It is an object of the invention to provide an improved combination gas and oil burner wherein this fouling is suppressed.

It has now been found that the aforesaid fouling can be entirely suppressed by giving the outer edge of the annular deflector that is in front of the annular gas channel a diameter that is larger than the inner diameter of the mouth of the gas supply tube and advantageously shaping the deflector so that the outer part of the rearward surface is substantially perpendicular to the axis of the burner.

It was found that even when liquid fuel is used for a considerable time in operating the burner according to the invention fouling does not occur. The recurrent cleaning of the gas burner, which was formerly necessary when the burner was switched from liquid fuel to gaseous fuel, can now be dispensed with. 6

in order to insure intimate mixing of the gas with the combustion air that is supplied externally of the gas supply tube, the deflector is preferably in the shape of a trumpet, in such a way that the outer end of its rearward face merges along a continuous curve with the inner, cylindrical wall of the gas supply passage. The outer wall of the gas passage is preferably cylindrical fully to the open end and this wall may have a flat,

atent M 2,808,876 Patented Oct. 8, 1957 annular end face. Further, the gas outlet may be provided with a series of vanes between the end face and the deflector inclined to the radial directions so as to impart a rotational movement to the externally merging gas.

The invention will be further illustrated by reference to the accompanying drawing forming a part of this specification and showing two specific embodiments by way of illustration, wherein:

Figure 1 is a diagrammatic longitudinal sectional view of the combination burner, parts being shown in elevation;

Figure 2 is an enlarged fragmentary view of the front part of Figure 1; and

Figure 3 is a view similar to Figure 2 showing a modifled embodiment including an air supply channel.

Referring to Figures 1 and 2, the burner comprises an outer annular, cylindrical wall or gas tube 5 provided with a lateral gas inlet 6 and closed at the rear by a wall 7. Concentric within and in radially spaced relation to the outer wall is an oil supply tube 8 which extends rearwards through the wall 7 and may be centered by suitable means, such as a plurality of thin radial lugs 9. An oil atomizer 10, such as a swirl type atomizer, is fitted to the front of the tube 8. In practice the rear wall 7 may be separate and provided with means sealing it to the tube 8 and for securing the latter in adjusted position; such means, being well understood in the burner art, need not be further described herein. It will be further understood that the outer tube 5 is mounted to extend through a breech in a furnace or combustion chamber with annular clearance through which combustion air is supplied in a generally forward direction 11, preferably with a swirling or helical motion as indicated by the arrow 12, produced by an air casing having suitable swirl blades or tangential inlets, as also are well known in the art.

An annular deflector 13 is fitted to the rear of the atomizer and is situated in front of the annular, forwardly directed outlet of the gas supply channel defined by the tubes 5 and 8. This deflector has an outer diameter that exceeds the inner diameter of the open front end of the outer tube 5 and the outermost part of the rearwardly directed deflecting surface lies substantially in a plane that is perpendicular to the axis of the burner.

According to a preferred embodiment, the difference a between the radius of the outer part of the deflector and the radius of the inner surface of the tube 5 is about 7% of the latterradius; the outer diameter of the deflector is, however, preferably not in excess of the outer diameter of the tube 5. It is preferred to shape the said deflecting surface as a trumpet, i. e., as a surface of revolution of a are about the axis of the burner, as shown, whereby the said surface extends as a smooth, continuous curve from the outer surface of the tube 8 to the said outermost part of the deflector. The center of curvature of said are is suitably at or near the front, inner edge of the tube 5 (e. g., as indicated at b, Figure 2), whereby the gas can flow without restriction. Further, it is preferred to avoid throttling rings, baffles or other obstructions in the annular gas supply channel, which thereby has throughout its length a substantially constant cross sectional area; pressure losses are reduced in this way.

When operating on liquid fuel, such as oil, the fuel is supplied to the rear of the supply tube 8 under suitable pressure in the direction of the arrow 14 and is atomized in the swirl chamber atomizer 10 to form a cone 15. The atomized liquid comes into contact with the air moving externally of the tube 5, as indicated by the arrow 12 and is burned. When operating on gaseous fuel, combustible gas or a gaseous mixture thereof with primary combustion air is admitted to the gas inlet 6, in the direction indicated by the arrow 16, passed through the annular gas supply channel between the tubes 5 and 8, and deflected by the trumpet-shaped deflector 13 to emerge in all radial directions substantially perpendicular'to the axis of the burner, as indicated by the arrows 17. Y The gas burner is, therefore, of the ring type and directs the gas essentially perpendicularly to the axis 11 of the flow path 12 of combustion air.

The trumpet-shaped deflector 13 serves, apart from deflecting the gas, during operation as a gas burner, to prevent liquid droplets issuing from the cone 15 during operation as a liquid fuel burner from being carried into the space between the tubes 5 and 8, where they would otherwise partly carbonize and form deposits on the walls. Such deposition and carbonization of liquid fuel during operation on liquid fuel would result in fouling of the gas supply channel and the outlet thereto to such an extent that the burner could not be switched to gas until the gas burner has been cleaned. This arrangement makes it possible to have the gas supply channel totally unrestricted.

In the embodiment shown in Figure 3, wherein like reference numbers denote like or corresponding parts, .the oil supply tube 8 and atomizer 10 are surrounded by an air supply tube 18 that is concentric to the burner axis and is spaced both from the tubes 5 and 8. The annular gas conduit is, in this instance, formed by the tubes 5 and 18 while air may be admitted through the annular channel between the tubes 8 and 18, as indicated by the arrow 19, when the burner is in operation using liquid fuel. This air current prevents the formation of soot and deposits of coke on the atomizer 10. The deflector 13a isin this embodiment fitted at the end of the tube 18 (it may be integral or separate) which, as before, has a trumpet-shaped rearwardly directed deflecting surface directly in front of the opening at the front of the annular gas supply channel and has a diameter in excess of the internal diameter of the tube 5. The deflector performs the functions previously described. This embodiment has the advantage that cleaning of the oil burner during operation no longer presents any difficulties; the atomizer 10 and tube 8 can be Withdrawn toward the rear while the gas burner is in operation.

I claim as my invention:

1. A burner including: a liquid fuel atomizer for discharging atomized liquid fuel forwards; a liquid fuel supply tube for said atomizer; supply conduit means including an outer annular wall having a thickness small in relation to the diameter thereof disposed concentrically about said liquid fuel supply tube and providing at the front an annular, forwardly directed outlet, the outer surface of said outer annular wall being exposed for the forward flow of air near said outlet; means for .flowing air forwardly about said conduit means; an annular deflector having a deflecting surface situated in front of and facing said outlet and rearwardly of the front of said atomizer, the outer part of said deflector having a diameter in excess of the inner diameter of the front end of said annular wall, and the outer part of said deflecting surface lying substantially in a plane that is perpendicular to the axis of said atomizer.

2. A burner according to claim 1 wherein said deflecting surface has a trumpet-shape and extends as a continuous curve from the inner limit of said annular outlet to said outer part of the deflecting surface.

3. A combination burner according to claim 1 including an air tube situated concentrically within said outer Wall and in spaced relation thereto and to said liquid 7 fuel supply tube to define within itself an air supply conduit having an annular opening at the front surrounding the said atomizer, said supply conduit means being constituted by said air supply conduit and said outer annular wall, and said deflector being fitted to the end of said air supply tube.

4. A burner according to claim 3 wherein said deflecting surface has a trumpet-shape and extends as a continuous curve from said air tube to the said outer part of the deflecting surface.

5. A burner according to claim 1 wherein said supply conduit means includes an inner wall inside of said outer annular wall, said inner and outer walls being spaced apart at a substantially constant distance throughout the length of the burner, thereby to define an annular channel of substantially constant cross section.

6. A burner including: a liquid fuel atomizer for discharging atomized liquid fuel forwards; a liquid fuel supply tube for said atomizer; a supply tube having a wall thickness small in relation to the diameter thereof disposed concentrically about said liquid fuel supply tube and providing at the front an annular, forwardly directed outlet, the outer surface of said supply tube being exposed and unobstructed for the flow of air near said outlet; means for flowing air forwardly about said supply tube; an annular deflector having a deflecting surface situated in front of said outlet and rearwardly of the front of said atomizer, the outer part of said deflector having a diameter in excess of the inner diameter of the tube and not in excess of the outer diameter thereof, and said deflecting-surface having a trumpet-shape and extending as a continuous curve from the inner limit of the annular outlet to said outer part of the deflector, the outermost part of said surface lying substantially in a plane that is perpendicular to the axis of the atomizer.

References Cited in the file of this patent UNITED STATES PATENTS 1,671,494 Stewart May 29, 1928 1,879,916 Bagley Sept. 27, 1932 2,216,508 Zink Oct. 1, 1940 2,474,313 Hess June 28, 1949 2,543,617 Wiant Feb. 27, 1951 2,670,788 MacFarlane Mar. 2, 1954 

